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70 lines
3.7 KiB
Markdown
70 lines
3.7 KiB
Markdown
# Example (JKQTPlotter): Parametrized Scatter-graph with custom symbols {#JKQTPlotterparamscatterCustomSymbol}
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This project (see `./examples/paramscatterplot_customsymbol/`) demonstrates using JKQTPlotter to draw a parametrized scatter graph (JKQTPXYParametrizedScatterGraph) with custom symbols. To demonstrate this, we create a plot with several symbols, connected by a line, where each symbol shows a pie-chart with varying fractions.
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The source code of the example can be found in [`paramscatterplot_customsymbol.cpp`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/paramscatterplot_customsymbol/paramscatterplot_customsymbol.cpp).
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First we create a plotter window and get a pointer to the internal datastore (for convenience). Then we add three new datacolumns and obtain back inserters.
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```.cpp
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JKQTPlotter plot;
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JKQTPDatastore* ds=plot.getDatastore();
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size_t columnX=ds->addColumn("x");
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auto colXInserter=ds->backInserter(columnX);
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size_t columnY=ds->addColumn("y");
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auto colYInserter=ds->backInserter(columnY);
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size_t columnS=ds->addColumn("sym");
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auto colSInserter=ds->backInserter(columnS);
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```
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Now we define a functor that draws a pie chart with three segments with fractions `f1` (blue), `f2` (green) and `1.0-f1-f2` (yellow):
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```.cpp
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auto pieFunc=[](QPainter& p, double f1, double f2) {
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double f3=1.0-f1-f2;
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QRectF rec(-0.5,-0.5,1,1);
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p.setPen(QPen(QColor("black"), p.pen().width(), Qt::SolidLine));
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p.setBrush(QBrush(QColor("blue")));
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p.drawPie(rec, 90, -f1*360*16);
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p.setBrush(QBrush(QColor("green")));
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p.drawPie(rec, 90-f1*360*16, -f2*360*16);
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p.setBrush(QBrush(QColor("yellow")));
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p.drawPie(rec, 90-(f1+f2)*360*16, -f3*360*16);
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};
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```
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Now we create data for the plot, x and y follow a simple function and the symbols are encoded in a separated column, where for each datapoint, we register a new symbol using JKQTPRegisterCustomGraphSymbol(), which is drawn by a differently parametrized (f1,f2) functor pieFunc.
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```.cpp
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const int Ndata=5;
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for (int i=0; i<Ndata; i++) {
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// put data
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const double x=double(i)/double(Ndata-1);
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*(colXInserter++)=x;
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*(colYInserter++)=pow(x*1.3, 2.0);
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*(colSInserter++)=JKQTPRegisterCustomGraphSymbol(std::bind(pieFunc, std::placeholders::_1, x*0.4, 0.5-x*0.2));
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}
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```
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Finally we create a graph in the plot, which displays our datasets:
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```.cpp
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JKQTPXYParametrizedScatterGraph* graph1=new JKQTPXYParametrizedScatterGraph(&plot);
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graph1->setXColumn(columnX);
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graph1->setYColumn(columnY);
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graph1->setSymbolSize(25);
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graph1->setDrawLine(true);
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graph1->setLineWidth(4);
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graph1->setDrawLineInForeground(false);
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graph1->setColor(QColor("black"));
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graph1->setTitle(QObject::tr("pie scatter"));
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```
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The symbol type is stored in columnS, note however how we have to give a custom JKQTPXYParametrizedScatterGraph::symbolColumnFunctor, because the default one maps the values in the column to the range `[0...JKQTPMaxSymbolID]` in a cycling fashion (using a mod operation), but here we want to use the `stored ID directly.
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```.cpp
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graph1->setSymbolColumn(columnS);
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graph1->setSymbolColumnFunctor(std::bind([](double /*x*/, double /*y*/, double symbolcolumn)->JKQTPGraphSymbols {
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return static_cast<JKQTPGraphSymbols>(floor(symbolcolumn));
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}, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3));
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plot.addGraph(graph1);
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```
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The result looks like this:
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